1. Technical Field
The present invention relates to a process for preparing high-quality aliphatic nitriles in high yields.
2. Description of the Prior Art
In general, aliphatic nitriles are industrially produced by the reaction of aliphatic carboxylic acids or derivatives thereof with ammonia. The reaction are broadly classified into gas-phase and liquid-phase processes. According to the gas-phase process, the reaction is conducted by preliminarily vaporizing an aliphatic carboxylic acid or a derivative thereof and bringing the vapor into contact with ammonia at a temperature of 250 to 600.degree. C. in the presence of a catalyst having a dehydrating activity, e.g., oxide of Zr, Ta, Ga, In, Sc, Nb, Hf, Fe, Zn or Sn (JP-A 4-208260), aluminum oxide, silica gel, thorium oxide or titanium oxide. However, the gas-phase process involves the vaporization of the starting material and are therefore disadvantageous in that the energy cost is higher than that of the liquid-phase process.
On the other hand, the reaction is also frequently conducted according to the liquid-phase process in a batch-wise or continuous manner by heat-melting an aliphatic carboxylic acid or a derivative thereof in the presence of a catalyst and bubbling gaseous ammonia thereinto. Known catalysts for the reaction include aliphatic carboxylic acid salts of cobalt (U.S. Pat. No. 2,493,637), iron and iron compounds (JP-A 58-39653), zinc oxide, kaolin (DE-C 704494), and so on. Although these catalysts exhibit high catalytic activities at a reaction temperature of 300.degree. C. or below, they are soluble in the reaction fluid, so that the use of such a catalyst involves the separation and recovery thereof from the reaction product by specific operations, which unfavorably brings about a lowering in the yield of distillation or an increase of waste.
An object of the present invention is to provide a process for preparing a high-quality aliphatic nitrile in a high yield at a low cost without the dissolution of a catalyst in the product, which comprises reacting an aliphatic carboxylic acid, a lower alkyl ester thereof or a fatty acid glyceride with ammonia in the presence of a solid catalyst which exhibits a high activity at a reaction temperature of 300.degree. C. or below and is difficultly soluble in the reaction fluid.